Internal combustion engines of the annular piston type are known from the above identified U.S. Pat. No. 7,905,221 B2 which discloses an internal combustion engine comprising a substantially cylindrical air chamber having a circumferential interior wall and a substantially round upper interior wall. The engine has an annular shaped combustion chamber having a substantially circular inner wall surface substantially concentric with the cylindrical air chamber and a substantially circular outer wall surface substantially concentric with the cylindrical air chamber. The engine further comprises a pre-combustion, fixed volume chamber in fluid communication with the annular shaped combustion chamber, and a substantially cylindrical piston comprising a first surface cooperatively configured to fit within the substantially cylindrical air chamber. The engine also comprises an air sump supply in communication with a compression chamber configured to receive compressed air there from. For a detailed description of the background art of Internal Combustion Engines reference is made to the above-identified U.S. Pat. No. 7,905,221 B2 without repeating it here.
It is a fact that a significant amount of heat is generated by combustion in the annular combustion chamber wall. The heat is cooled in the known annular piston engine by providing cooling channels in the engine block for cooling the cylinder wall.
It is therefore an object of the present invention to further improve the cooling of an internal combustion engine of the annular piston type. It is a particular aim to provide efficient cooling of the annular piston of such an engine.